Possible candidates must have O blood type, weigh less than 150 pounds, younger than 40, in good health, and not recently pregnant.

Doctors only need 25 percent of the liver and said it will grow back within six months.

"We just took his 5-month picture. Little different from the 4-month one. Yeah," Albers told WITI.

But instead of growing stronger and bigger, little Marcus is doing the opposite.

"The last couple weeks have been really rough. His health - he has as good day and then he has a bad day," Albers said.

Marcus suffers from Immunodeficiency 47 - a rare genetic disorder. There are just twelve known cases in the world passed down through the mother. Only baby boys are at risk of showing symptoms.

Baby Marcus

"My grandmother had all girls, my mom had all girls," said McLean.

The disease essentially attacks the liver - giving patients just weeks to live.

Unable to donate part of their own livers, McLean and Albers found a donor for Marcus. But shortly before the transplant was scheduled for Tuesday morning, April 2, they received devastating news. It was not a perfect match.

"We thought we'd be talking about him in surgery right now - and please have your prayers, because he is in surgery," McLean said.